1. Field of the Invention
The present invention relates to a solid state color image pickup apparatus using a solid state image sensor, such as a CCD (Charge Coupled Device).
2. Description of the Related Art
A so-called single chip color camera is well known, which obtains a color image signal by means of only one CCD image sensor. Since the single chip color camera, which is compact and light, is easy to handle and economically advantageous, it is utilized in image information input devices in various fields. The single chip color camera comprises optical color filters for light receiving elements on the CCD image sensor to separate color information from one another.
In the single chip color camera, conventional image signal processing means have the following structure. An optical image focused by an image pickup lens is imaged on an image pickup surface of the CCD image sensor through color filters. The CCD image sensor outputs an image signal corresponding to the optical image. The image pickup signal is amplified to a predetermined level by an amplifier. The amplified signal is converted to a digital signal by an A/D (analog/digital) converter.
The digital video signal output from the A/D converter is directly supplied to a color separator, and also 1H delayed by a 1H (horizontal scanning period) delay line and thereafter supplied to the color separator. The color separator performs a matrix process for Mg, G, Cy and Ye signals corresponding to the color elements of the color filters, thereby generating three primary color signals, G, B and R signals.
The three primary color signals are subjected to processes in a television camera, such as a white balance process and a gamma control. The three primary color signals are further subjected to a matrix process, and converted to a luminance signal Y and two color-difference signals (R-Y.sub.L) and (B-Y.sub.L). Y.sub.L is a low-pass component of the luminance signal Y. The two color-difference signals (R-Y.sub.L) and (B-Y.sub.L) are respectively supplied to the corresponding modulators.
A sub-carrier signal of 3.579545 MHz is phase-shifted by a phase shifter and supplied to the (R-Y.sub.L) modulator. Further, a sub-carrier signal of 3.579545 MHz is directly supplied to the (B-Y.sub.L) modulator. Therefore, the phase-shifted sub-carrier signal is modulated with the color-difference signal (R-Y.sub.L) by the (R-Y.sub.L) modulator and the sub-carrier signal is modulated with the color difference signal (B-Y.sub.L) by the (B-Y.sub.L) modulator.
Output signals from the (R-Y.sub.L) and (B-Y.sub.L) modulators are added together by an adder, and thereafter converted to an analog signal by a D/A (digital to analog) converter, so that a modulated color signal C.sub.A is generated. The aforementioned luminance signal Y is also supplied to the D/A converter and converted to an analog luminance signal Y.sub.A.
The modulated color signal C.sub.A and the luminance signal Y.sub.A are added to a color burst signal and a sync signal by another adder. As a result, a television signal of NTSC (National Television System Committee), one of the standard television systems, is generated.
As described above, to convert a video signal output from the CCD image sensor to a television signal of the NTSC system, the conventional video signal processing means perform a series of signal processes, in which the video signal is subjected to a color separating process to obtain three primary color G, B and R signals; the G, B and R signals are subjected to a process/matrix process to obtain a luminance signal Y and two color-difference signals (R-Y.sub.L) and (B-Y.sub.L); and the sub-carrier signal of 3.579545 MHz is subjected to quadrature modulation with the color-difference signals (R-Y.sub.L) and (B-Y.sub.L) to obtain a modulated color signal C.sub.A.
To execute the above series of signal processes, circuit blocks are inevitably required. For this reason, although the color camera uses a CCD image-pickup element, which is compact, light, low-power consuming and inexpensive, there is a problem that the size, weight, power consumption and cost of the camera itself cannot be sufficiently reduced.
Even if most of the signal processing circuit blocks are integrated as an IC to improve the integration density, the above problem cannot be practically solved, since the reduction of the size and weight, power consumption and cost of a camera is limited to a certain degree. The above problem is posed whether the signal processing in the camera is analog or digital, because the circuit blocks are required to perform the above series of signal processes in either case.
As described above, in the conventional video signal processing means in a color camera having a CCD image sensor, to convert a video signal output from the CCD image sensor to a television signal of the standard system, complicated signal processes are required. The conventional art therefore has a problem in that the reduction of the size, weight, power consumption and cost of the camera itself is limited.